Downhole valve

ABSTRACT

A downhole check valve includes a body (32) defining a flow passage and a valve assembly (34, 42, 44) mounted in the body, the valve assembly including a valve member (34) movable from a first configuration to a second configuration. In the first configuration the valve member prevents flow in one direction through the passage, and in the second configuration the valve member is retained in an open position. A valve member retaining sleeve (48) is normally restrained in a first configuration and biassed for movement to a second configuration. The retainer is held in the first configuration while the valve member (34) is in the first configuration and is releasable from the first configuration to move the valve member to the open position and retain the valve member in the open position.

This invention relates to a valve particularly useful in downholeapplications.

In the oil and gas exploration and production industry, drilled boresare lined with steel tubing which is secured in the bore with cement: inthe upper section of a bore a steel casing is provided; and a steelliner is provided in the lowermost section of the bore which intersectsthe oil or gas bearing strata, known as the production or pay zone. Inaddition, production tubing may be provided within the casing, forcarrying oil or gas to the surface from the production zone. The upperend of the production tubing is located relative to the casing by atubing hanger and the lower end of the tubing is located relative to thecasing by a packer, typically in the form of a flexible element mountedon the exterior of the production tubing and which is inflated to engagethe casing.

It is essential that the production tubing, formed of a large number oftubing lengths which have been threaded together, is pressure-tight, andalso that the tubing hanger is pressure tight. Further, the connectionbetween top of the liner and the lower end of the casing must be secureand pressure-tight. Testing the "completion" of the tubing and theintegrity of the liner/casing connection or liner hanger is achieved byproviding valves at appropriate locations in the tubing and liner andthen pressurising the tubing and liner above the respective valve usingpumps on the surface. The integrity of the tubing hanger is tested byblanking of the tubing and pressurising the annulus between the tubingand the casing below the hanger. A similar valve is also provided,between the valves mentioned above, to allow the packer to be set bypressurised fluid which passes through suitable ports in the tubingabove the closed packer setting valve to inflate the packer.

both the tubing and the liner are installed with the valves in position,located in suitable nipple profiles. The valves are normally closed butwill open in response to a pressure force from below such that wellfluid may flow into the tubing or liner as it is lowered into the bore.The tubing test valve is the first to be used, and may be utilised on anumber of occasions to test the completion of sections of productiontubing being added to the production string. When the entire productionstring is in place and has been tested, the valve is removed from thetubing using wireline, coil tubing or the like in conjunction with asuitable fishing tool. As mentioned above, the tubing hanger is testedby blanking off the tubing at the surface and pressurising the annularbetween the tubing and the casing below the hanger.

The packer is then set by pumping down on the packer setting valve. Oncethe packer has been set, the valve is removed from the tubing.

Finally, the integrity of the liner/casing connection is checked bypumping down on the top of the liner test valve. This lowermost valve isthen removed.

The valves used for these applications are running standing valves and,as noted above, the valves must be removed from the tubing and the linerafter use. This involves at least three runs of wireline or the like,and experience has shown that for various reasons the valves are oftendifficult to remove, and even straightforward valve removal operationstake a considerable time to complete. Coupled with the requirement toprovide a wireline or coil tubing rig and operator, and resulting valveremoval operation is thus relatively expensive and time-consuming,particularly in offshore operations.

It is among the objects of embodiments of the present invention toobviate or mitigate these disadvantages.

According to one aspect of the present invention there is provided adownhole valve including:

a body defining a flow passage;

a valve assembly mounted in the body, the valve assembly including avalve member being movable from a first configuration to a secondconfiguration, in the first configuration the valve member preventingflow in at least one direction through the passage, and in the secondconfiguration the valve member being retained in an open position; and

a valve member retainer normally restrained in a first configuration andbiased for movement to a second configuration, the retainer being heldin the first configuration while the valve member is in the firstconfiguration and being releasable from said first configuration to movethe valve member to the open position and retain the valve member in theopen position.

The invention permits use of a valve which is fixed in a length oftubing in applications where the valve is only required for, forexample, initial testing of the pressure-tightness of the tubing. Withthe present invention the valve may be utilised initially in the firstconfiguration as a check valve and then, once testing is completed, thevalve member is moved to the second configuration to allow unrestrictedflow through the tubing such that there is no requirement to remove thevalve from the tubing. Embodiments of the present invention may serve astubing test vales, packer setting valves, or top of liner test valves,as will be described.

Preferably, in the first configuration, the valve member is normallyclosed and will hold pressure from said one direction but will open inresponse to pressure from the opposite direction. This permits the valveto be utilised in completion testing, where the valve must hold pressurefrom the surface side but opens in response to pressure from the sumpside, to permit the tubing to fill with well fluid as it is lowered intoa bore.

Preferably also, the valve member retainer is biassed towards its secondconfiguration by a spring.

Preferably also, the valve member retainer is released from its firstconfiguration by axial movement of the valve assembly relative to thevalve body. The axial movement of the valve assembly may result inrelease of a trip coupling, such as trip keys. The axial movement may beachieved by application of a pressure force to the valve member or to aportion of the valve assembly. In one embodiment the pressure force maybe applied directly to the valve member by fluid in the tubing, while inanother embodiment the pressure force may be applied by a separatesource of fluid pressure, such as an explosive charge.

Axial movement of the valve assembly relative to the body may beresisted by a biassing member, such as a spring. The biassing member maythus be pre-stressed such that the degree of axial movement necessary torelease the valve member retainer is only obtained by application of apressure above a predetermined level to the valve member or valveassembly. Alternatively, or in addition, the valve assembly may beinitially coupled to the body to prevent relative movement therebetweenand may be uncoupled to permit release of the valve member retainer. Inone embodiment the coupling may be in the form of a shear coupling orother coupling that will release on application of a predeterminedforce. Alternatively, the coupling may include a coupling member whichmay be retracted or otherwise configured to permit uncoupling;preferably, a coupling member actuator is provided and may be remotelyactivated to permit uncoupling. In one embodiment the coupling memberactuator is an electric motor which may be activated by pressure pulses.

Preferably also, the valve assembly includes a portion for closing aport in the wall of the body, which port may communicate with a controlline linked to a packer or other fluid actuated downhole tool. The valveassembly portion initially closes the port but is movable to permitfluid flow through the port from the body passage.

Preferably also, the valve assembly includes a valve member carriage andthe released retainer is movable relative thereto. Where the valvemember is a ball, the carriage may include a ball cage and the releasedretainer may be movable relative to the cage.

Preferably also, the retainer includes an axially movable sleevedefining a portion of the valve flow passage. Where the valve is a ballvalve, an end of the sleeve may contact the ball surface and push theball to the open position. Where the valve member is in the form of oneor more flappers, an end of the sleeve may push the flappers to the openposition and then define the flow passage past the flappers.

In one embodiment of the invention, the valve member ay be configured topermit limited flow of fluid in said one direction. This may be achievedby providing a further valve including a normally open valve memberwhich remains open where there is only a limited flow in said onedirection, but closes in response to a higher rate of flow. Such a valvemay include a valve member which is normally lifted from its seat by aspring, such that fluid may pass around the member. However, a higherflow creates a pressure force on the valve member and overcomes thespring force to close the valve. Conveniently, the valve member is inthe form of a ball. This further valve may be provided in the main valvemember, as described above. Alternatively, a normally open ball valvemay be provided in combination with a valve actuator defining a piston,venturi or other restriction above the ball; a restricted flow of fluidwill pass through the valve, but a greater flow rate will create apressure force to push the ball to the closed position. Theseembodiments have particular application in situations where two valvesare provided in a length of tubing and the upper valve will be used andthen moved to the open second configuration before utilising the secondvalve. If the second valve is one which may be moved to the secondconfiguration in response to fluid pressure applied from the fluid inthe tubing, there is a risk that any leakage past the first valve willcause the second valve to move to the open second configuration.Providing an additional normal open valve in the second valve obviatesthis risk, as any leakage will simply pass through the second valve,avoiding any pressure build in between the valves. However, once thefirst valve has been opened, a higher flowrate will close the normallyopen valve and permit the second valve to operate as normal, and alsopermit movement of the second valve to the second configuration.

In accordance with another aspect of the present invention there isprovided a downhole check valve comprising:

a body defining a flow passage;

a valve assembly mounted in the body, the valve assembly including: aprimary valve member being movable from a first configuration to asecond configuration, in the first configuration the valve memberpreventing flow in at least one direction through the passage, and inthe second configuration the valve member being retained in an openposition; and a normally open secondary valve member configured topermit flow in said one direction through said primary valve member upto a predetermined rate and being closed by fluid forces in the event ofthe flow rate approaching said predetermined rate. Preferably, thesecondary valve member is located on the primary valve member andcontrols flow through a passage extending therethrough.

According to another aspect of the present invention there is provideddownhole apparatus including:

a body;

a member mounted on the body and being movable relative thereto;

a coupling between the body and the member, in a first configuration thecoupling preventing movement of the member relative to the body and in asecond configuration the coupling permitting such movement;

a coupling actuator for moving the coupling from the first to the secondconfiguration;

a sensor operatively associated with the coupling actuator and foractivating the actuator on detection of a predetermined activationsignal.

The member may be part of a valve, the valve being locked in a closedfirst configuration by the coupling and being movable to an open secondconfiguration on reconfiguring of the coupling. The valve may controlflow of fluid through an axial passage defined by the body, or maycontrol flow of fluid through a wall of the body, for example between anaxial body passage and an annulus between the body and a drilled borewall or between a body passage and a control line extending to a furthertool, for example a packer.

The member may be movable by application of fluid pressure thereto.

The coupling actuator may include an electric motor. The motor may belinked to a threaded shaft and threaded follower for movementtherealong.

These and other aspects of the invention will now be described, by wayexample, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of a portion of a well including atubing test valve, a packer setting valve, and a top of liner testvalve;

FIG. 2 is a sectional view of a check valve in accordance with a firstembodiment of the present invention, suitable for use as a top of linertest valve, shown in a normally-closed first configuration;

FIG. 3 shows the valve of FIG. 2 in a fully-open second configuration;

FIG. 4 is a sectional view of a check valve in accordance with a secondembodiment of the present invention, suitable for use as a top of linertest valve, and illustrating the valve in a normally-closed firstconfiguration;

FIG. 5 shows the valve of FIG. 4 moving towards a fully-open secondconfiguration;

FIG. 6 shows the valve of FIG. 4 in the fully-open second configuration;

FIG. 7 is a sectional view of a check valve in accordance with a thirdembodiment of the present invention, suitable for use as a packersetting valve, and showing the valve in a normally-closed firstconfiguration;

FIG. 8 shows the valve of FIG. 7 moving towards a fully-open secondconfiguration;

FIG. 9 shows the valve of FIG. 7 in the fully-open second configuration;

FIG. 10 is a sectional half view of a check valve in accordance with afourth embodiment of the present invention, suitable for use as a packersetting valve, and showing the valve in a normally-closed firstconfiguration;

FIG. 11 is an enlarged scrap view of area 11 of FIG. 10;

FIG. 12 is a sectional view of a check valve in accordance with a fifthembodiment of the present invention, suitable for use as a tubing testvalve, and shown in a normally-closed first configuration;

FIG. 13 shows the valve of FIG. 12 in a fully-open second configuration;

FIG. 14 is a sectional view of a check valve in accordance with a sixthembodiment of the present invention, suitable for use as a packersetting valve and a tubing test valve; and

FIGS. 15 and 16 are sectional scrap views of a part of a check valve inaccordance with a seventh embodiment of the present invention.

Reference is first made to FIG. 1 of the drawings which illustrates,somewhat schematically, a section of oil production well bore 10. Thisenvironment will be used to describe examples of applications for valvesin accordance with embodiments of the present invention. The upperportion of the drilled bore 10 is lined by a steel casing 12. The lowerend of the bore 10, which intersects the oil bearing strata, known asthe production or pay zone, is provided with a steel liner 14 which isconnected to the lower end of the casing 12. Oil is carried to thesurface from the production zone through production tubing 16 locatedwithin the casing 12. The upper end of the tubing 16 is located relativeto the casing 12 by a tubing hanger 17 and lower end of the tubing 16 islocated relative to the casing 12 by a packer 18.

Before production from the bore 10 commences, the operator will wish totest the pressure integrity or "completion" of the production tubing 16,inflate the packer 18, and also test the integrity of the annular sealsprovided by the liner hanger and tubing hanger 20 between the top of theliner 14 and the lower end of the casing. These operations utilisetubing test valve 22, a packer setting valve 24 and a top of liner testvalve 26, respectively, in accordance with embodiments of the presentinvention. Each valve is a normally-closed check valve which allows flowof fluid upwardly as the liner 14 or production tubing 16 is loweredinto the bore, but prevents flow of fluid down the bore. The valves areused in sequence as follows. Firstly, the completion of the productiontubing 16 is tested by pumping down onto the tubing test valve 22 up toa pressure of 5000 psi. The valve 22 effectively seals the lower end ofthe tubing 16, such that any loss of pressure indicates a loss of wellfluid at some point along the tubing 16. This operation may take placeon numerous occasions as new sections of tubing are added at the surfaceand the end of the tubing 16 moves down through the bore 10. Once thetubing 16 is complete, the tubing test valve 22 may be moved to a fullyopen position, this feature of the valve being one of the main aspectsof the present invention. The packer setting valve 24 is now in fluidcommunication with the surface, such that fluid may be pumped down thetubing 16 on top of the valve 24, up to 2000 psi, to inflate the packer18. Once the packer 18 has been set, the valve 24 is moved to thefully-open position. It is now possible to test the integrity of theconnection 20, and ensure that the packer 18 has been properly set, bypumping down the production tubing 16 onto the top of liner valve 26.Once testing has been completed the valve 26 is moved to the fully-openposition.

Reference is now made to FIGS. 2 and 3 of the drawings, which illustratea check valve 30 in accordance with a first embodiment of the presentinvention. The valve 30 is suitable for use as a top of liner test valve26, as will be described. The valve 30 comprises a tubular body 32having ends suitable for connection to adjacent liner sections. The body32 accommodates a ball valve assembly including a ball 34 defining aflow passage 35. A pusher sleeve 36 mounted within the body 32 defines aportion of the flow passage through the body 32 and contacts the uppersurface of the ball 34. The sleeve 36 is biased by a spring 38 to pushthe ball 34 towards the closed position, as illustrated in FIG. 2. Whenclosed, the ball 34 engages a roller seat 40 and a ball seat 42 formingpart of a ball valve carriage 43 including a ball cage 45. In normalconditions, further downward movement of the ball 34 is prevented by aball support sleeve 44 which is supported relative to the valve body 32by a shear ring 46.

When the valve 30 is run into the bore 10 in the liner 14, the wellfluid below the normally-closed valve 30 pushes the ball 34 upwardlysuch that the ball rotates and well fluid may flow in direction A,through the flow passage 35 and into the liner above the valve 30. Oncethe liner is in position, and pressure equalises across the valve 30,the ball 34 returns to the closed position. The integrity of theconnection 20 and the packer 18 may then be tested by pumping down onthe closed valve 30. However, once testing has been completed, the ball34 may be moved to a fully-open position as described below.

Provided below the ball 34 is a ball retaining sleeve 48 which defines aportion of the valve flow passage. The sleeve 48 is biased upwardly by aspring 50, formed of Bellville washers. However, when the valve 30 is inthe normally-closed first configuration, the sleeve 48 is restrained ina first position relative to the ball support sleeve 44 by keys 52 whichextend into a groove 54 formed in the outer surface of the sleeve 48,the keys 52 being located within a sleeve 56 connected to the ballsupport sleeve 44.

To release the ball retaining sleeve 48, pressure is applied indirection B, the applied pressure exceeding the normal test pressure.This pressure acts over the upper surface of the ball 34 to produce aconsiderable downward pressure force such that the ball and itssupporting structure will move downwardly as a "ball piston". The forceis selected to be sufficient to compress the spring 50 and to shear thering 46, permitting the ball support sleeve 44, the key mounting sleeve56 and the ball retaining sleeve 48 to be pushed downwardly relative tothe valve body 32. This movement continues until the trip keys 52 alignwith a trip key groove 58 formed in a portion of the valve body 32. Thetrip keys 52 move into the groove 58, thus releasing the ball retainingsleeve 48 from the sleeves 44, 56. Pressure is then bled off from abovethe ball 34, such that high rate spring 50 pushes the ball 34 upwardly,to rotate the ball to the fully-open position, as illustrated in FIG. 3of the drawings. Once moved to the fully-open position, the ball 34 doesnot respond to fluid pressure within the valve 30, such that the ball 34will remain in the fully open position under the action of the spring50. However, if considered necessary, a positive locking device, such asa latch, may be provided to hold the ball retaining sleeve 48 inposition.

Reference is now made to FIGS. 4, 5 and 6 of the drawings, whichillustrate a check valve 60 in accordance with a second embodiment ofthe present invention. This valve 60 is also suitable for use as a topof liner test valve 26. The valve 60 operates in a similar manner to thecheck valve 30 as described above, however this particular embodiment isin the form of a flapper valve and thus includes a flapper 62 mounted ona pivot pin 64 including a spring 66 which tends to close the flapper62. The flapper seat 68 is formed at the upper end of a flapper supportsleeve 70 itself supported on a shear ring 72, in a similar manner tothe valve 30 described above.

As with the valve 30, the check valve 60 may be used in the firstnormally-closed position to check the integrity of the connection 20 andthe packer 18 by pumping down on the normally closed valve. However, tomove the valve to the fully-open second configuration, a higher pressureis applied which acts on the upper face of the flapper 62 to move thevalve piston downwardly with respect to the valve body. The resultingpressure force shears the ring 72, allowing the valve piston to movedownwardly to release trip keys 74 such that the flapper retainingsleeve 76 may be pushed upwardly by the spring 78 and move the flapper62 to the fully-open position, and also to isolate the flapper within anannular chamber 80, as illustrated in FIG. 6 of the drawings.

In the event that, for some reason, the valve 60 fails to close fullyand thus cannot be pushed downwardly by an over pressure to allowrelease of the flapper retaining sleeve 76, the upper end of the bodydefines a nipple profile 82 and polished bore to allow a prong to belowered into the bore and mounted on the valve 60. The probe may then beused to force the flapper 62 to close, and/or push the valve pistondownwardly to release the retaining sleeve 76.

A nipple profile and polished bore may be provided on any of theembodiments described herein, and is also illustrated in the embodimentshown in FIGS. 7, 8 and 9.

Reference is now made to FIG. 7, 8 and 9 of the drawings, whichillustrate a check valve 84 in accordance with a third embodiment of thepresent invention. The check valve 84 is generally similar to the checkvale 60 described above but is provided with a somewhat different valveflapper 86 such that the valve may be utilised as a packer setting valve24. The flapper 86 itself accommodates a normally-open valve 88 whichcomprises a flow passage 90 and a ball 92 restrained within a cage 94.The ball 92 is normally lifted from its seat by a coil spring 96. Theball 92 is formed of a material such as bakelite, or some other brittlematerial; when the flapper 86 is pushed open, as will be described, theball will shatter. This allows provision of a relatively large ball,which will provide a more effective seal when closed, and which wouldotherwise prevent the flapper 86 from moving to the fully-open positionwithin the chamber 80.

The valve 84 is normally-closed, and like the check valves 30, 60described above, is moved from the normally closed first configurationto the fully-opened second configuration by application of an overpressure. However, as the valve 84 is to be utilised as a packer settingvalve 24, the valve 84 will be located below a tubing test valve 22. Inuse, the tubing test valve 22 will be used in its normally-closed firstconfiguration for testing the completion of the production tubing 16,and then moved to the fully-open second configuration before the valve84 is used. If, for example, the valve 60 as described above, was usedas the packer setting valve 24, there would be a danger that, while thecompletion of the production tubing 16 was being tested, any leaks pastthe tubing test valve 22 would result in a build up of pressure betweenthe valves 22, 24, which pressure could be sufficient to set the packerprematurely or to move the packer setting valve to the open secondconfiguration. This potential problem arises, in part, due to therelatively low pressures used to set the packer (2000 psi) and thehigher completion testing pressure (5000 psi). This difficulty isavoided by the provision of the normally-open valve 88 in the valveflapper. In the event of leakage past the tubing test valve 22, thesmall volume of fluid which passes through the valve 22 will simply passthrough the normally open valve 88 and thus there will be no pressurebuild up above the check valve 84. However, once the tubing test valve22 has been moved to the fully open second configuration, pumping downon the check valve 84, for example at a flowrate of 2 barrels perminute, will push the ball 92 onto its seat and close the flow passage90. Pressure may then be applied to the valve 84 to set the packer 18,and then a further higher pressure may be applied to the valve 84 torelease the flapper retaining sleeve and move the valve to thefully-open second configuration. FIG. 8 of the drawings illustrates theposition of the valve piston shortly after it has commenced moving underinfluence of the over pressure, while FIG. 9 shows the valve in thefully open configuration.

The embodiment of FIGS. 7, 8 and 9 incorporate a flap valve, but theprinciple of providing a valve which will not be activated by leakage ofthe valve above may also be applied to ball valves. Such a check valve130 is illustrated in FIGS. 10 and 11 of the drawings. It will be notedthat the valve 130 includes a ball element 132 defining a flow passage134 and also a smaller cross-section leakage passage 136 extendingnormal of the flow passage 134. The passage 136 extends through thewalls of the ball 132 on opposite sides of the flow passage 134 and isaligned with the longitudinal axis of the valve body when the valve isin the normally-closed first configuration, as illustrated in FIG. 10.One portion of the passage 136a includes a normally-open valve 138including a valve member 140 normally lifted from a valve seat 142 by acoil spring 144. As with the valve 84 described above, a small volumeflow of fluid may pass around the member 140 and thus through the valve130, whereas any significant flow of fluid with push the valve member140 against the seat 142, thus permitting a build-up of pressure abovethe ball 132.

Reference is now made to FIGS. 12 and 13 of the drawings, whichillustrate a check valve 100 in accordance with a fifth embodiment ofthe present invention, suitable for use as a tubing test valve 22. Thevalve 100 is substantially similar to the valve 30 described above.However, for this application the valve 100 will have to withstandcompletion testing pressures on a number of occasions up to the testingpressure for the tubing 16, typically 5000 psi. Clearly, if the valve100 was to be moved to the fully-open second configuration by an overpressure this would require that the over pressure was in excess of 5000psi and above the normally testing limit of the tubing 16. To avoid thisdifficulty, the valve 100 is provided with other means for moving thevalve to the second configuration, as will be described. The higherpressure capability of the valve 100 is accomplished simply by providinga shear ring 102 of a higher rating, for example, one which wouldwithstand application of an over pressure of 6000 psi before shearing.

Mounted towards the upper end of the valve body 104 is an intelligentsensor 106 in fluid communication with the valve flow passage 108. Ifthe sensor 106 detects a predetermined pressure signature (for example5000 psi for five minutes, then 3000 psi for three minutes) within theflow passage 108, an explosive charge 110 is detonated to create a veryhigh pressure in the chamber 112 which accommodates valve spring 114,and a lower wall of which is formed by the ball pusher sleeve 116.Detonation of the charge 110 results in a high pressure force beingapplied to the sleeve 116, such that the ball 118 and the lower ballsupport and retaining sleeves 119, 120 are pushed downwardly to trip theretaining keys 122, allowing the high rated spring 124 to push the ball118 to the fully-open second configuration, as illustrated in FIG. 13.

Reference is now made to FIG. 14 of the drawings which illustrates avalve 150 in accordance with a sixth embodiment of the presentinvention, suitable for use as a packer setting valve and also as atubing test valve; the valve 150 may be positioned in a similar mannerto the packer setting valve 24 as illustrated in FIG. 1, and thepresence of the valve obviates the need to provide a separate tubingtest valve 22. The valve 150 shares a number of features with the valvesdescribed above and comprises a tubular body 152 having ends suitablefor connection to adjacent tubing sections. The body 152 accommodates aball valve assembly including a ball 154 defining a flow passage 155.The ball 154 is similar to the ball element 132 described above and asillustrated in FIGS. 10 and 11 of the drawings, in the that the ball 154defines a smaller cross-section leakage passage 156 extendingperpendicular to the flow passage 155. One portion of the leak passage156a includes a normally-open valve 158 including a valve member 160normally lifted from a valve seat by a spring. A small volume of fluidmay pass around the member 160, whereas any significant flow of fluidwill push the valve member 160 against its seat, thus permitting abuild-up of pressure above the ball 154.

A pusher sleeve 166 mounted within the body 152 defines a portion of theflow passage through the body 152 and contacts the upper surface of theball 154. The sleeve 166 is biassed by a spring 168 to push the ball 154towards the closed position, as illustrated in FIG. 14. When closed, theball 154 engages a sleeve 170 including a ball seal 172. The sleeve 170is coupled to a ball cage 174 which is itself coupled to a lockingsleeve 176 that extends above the ball 154, between the pusher sleeve166 and the body 152. The upper end of the sleeve 176 defines springfingers 178 with enlarged ends which are normally locked relative to thebody 152 by engagement with keys 180 located in circumferentially spacedapertures in a sleeve 184 fixed to the body 152. With the ball assemblyin the initial normally-closed configuration, the locking sleeve 176extends across and closes a port 186 in the body sleeve 184, which port186 communicates with a control line 188 leading to a packer 18 (FIG.1). As the fingers 178 are locked relative to the body 152 by the keys180, the ball cage 174 is effectively locked relative to the body 152.However, the ball 154 is free to move upwardly and rotate to an openposition, against the action of the spring 168, in response to pressurebelow the ball 154.

To allow the keys 180 to move radially outwards, to release the ballcage 174 relative to the body 152 such that the valve may be moved tothe open configuration, a key support 190 is moved upwardly in the body152. The key support 190 is mounted on a threaded rod 192 linked to anelectrical motor 193 housed within a bore 194 formed in the body 152.The bore 194 also accommodates a suitable power cell for the motor. Theelectric motor is activated by a sensor which detects pressure pulses inthe tubular string, in a similar manner to the embodiment describedabove and as illustrated in FIGS. 12 and 13. On detecting thepredetermined sequence of pressure pulses, sometimes referred to as thepressure signature, the electric motor is activated and rotates the rod192 to lift the support 190 until the annular groove 196 defined by thesupport 190 is adjacent the keys 180. Pressurising the tubing above theball 154 will then cause the sleeve 176, ball cage 174, sleeve 170 andthe ball 154 to move downwardly relative to the body 152.

An initial degree of movement brings a port 198 in the locking sleeve176 into alignment with the port 186 in the body sleeve 184. This allowsfluid within the tubing bore to flow through the port 186 and controlline 188 to inflate the associated packer.

The lower end of the valve sleeve 170 engages the upper end of a springin the form of a stack of Bellville washers 200 such that, after releaseof the fingers 178, the pressure force applied to the ball "piston" mustbe sufficient to compress the stack 200 before the ball 154 and valveassembly will move downwards.

In common with the other ball valves embodiments described above, a ballretaining sleeve 202 is provided below the ball 154 and defines aportion of the valve flow passage. The sleeve 202 is biassed upwardly bya compression spring 204. However, the sleeve 202 is initiallyrestrained in a first position relative to the ball support sleeve 170by keys 206 which engage a shoulder 208 formed in the outer surface ofthe sleeve 202, the keys 206 being located in apertures 210 formed inthe lower end of the ball support sleeve 170; once the locking sleeve176 has been released from the body 152 as described above, the valve150 is opened in a similar manner to the ball valve embodiments asdescribed above, that is the sleeves 170, 202 are pushed downwards untilthe keys 206 move out into a lower groove 211 formed in a portion of thebody, permitting the sleeve 202 to move upwards, under the influence ofthe spring 204, relative to the sleeve 170 and ball cage 174, to pushthe ball into the open position.

The valve 150 also includes a lock open feature, the lower end of thesleeve 202 defining fingers 212 which engage in an annular slot 214formed in the inner wall of the body 152 when the sleeve 202 is movedupwardly, and thus prevent the sleeve 202 from being moved downwardlyrelative to the body 152.

Reference is now made to FIGS. 15 and 16 of the drawings, whichillustrate part of a check valve 220 in accordance with a seventhembodiment of the present invention. The valve 220 is substantiallysimilar to the valve 150 described above and operates in a substantiallysimilar manner and common reference numerals will be used to identifythe corresponding elements of the valve 220. The primary differencebetween the valves is the manner in which the valve opens once thesleeve 202 has been released; in the valve 150, and the other valvesdescribed above, the spring 204 pushes the sleeve 202 upwardly androtates the ball 154 once the pressure utilised to push the valveassembly downwards to release the sleeve 202 has been bled off at thesurface. However, in the valve 220 a fluid equalising path is providedto permit pressure equalisation across the ball 154, as described above.

FIG. 15 illustrates the valve 220 in the first configuration, with thesleeve 202 restrained against upward movement relative to the sleeve 170by the retaining key 206 engaging the shoulder 208. With the valve inthe first configuration, the lower surface of the ball 154 contacts thesleeve valve seal 172, while sleeve 170 is in sealing contact with thebody 152 via a pair of body-mounted `T` seals 222 (it will be noted thata similar sealing arrangement is present in the valve 150 describedabove). However, as the sleeve 202 is released and moves upwards underthe influence of the high-rated spring 204 (not shown in FIGS. 14 and15) it is desired to provide a fluid path around the ball 154 to permitpressure equalisation across the ball. To this end, the sleeve 170defines a port 224 intermediate to seals 172, 222 which, when the sleeve202 is restrained relative to the sleeve 170, is closed by a portion ofthe sleeve 202. However, on release of the sleeve 202 and following adegree of relative upward movement of the sleeve 202, a port 226 in thesleeve 202 is brought into alignment with the port 224, as illustratedin FIG. 16: this provides a fluid path around the ball 154. When theupward force provided by the spring 204 is greater the remainingdownward pressure force on the ball 154, the sleeve 202 pushes the ball154 into the open position.

This feature may be incorporated in any of the other valves describedabove, and offers a number of advantages, in particular the equalisationfeature facilitates opening of the valve when the pressure force createdby the column of fluid in the tubing above the valve exceeds thepressure in the well fluid below the valve.

It will be clear to those of skill in the art that the above-describedembodiments are merely exemplary of the present invention, and thatvarious modifications and improvements may be made thereto, withoutdeparting from the scope of the invention.

What is claimed is:
 1. A downhole valve including:a body defining a flowpassage; a valve assembly mounted in the body, the valve assemblyincluding a valve member being movable from a first configuration to asecond configuration, in the first configuration the valve memberpreventing flow in at least one direction through the passage, and inthe second configuration the valve member being retained in an openposition; a valve member retainer normally restrained in a firstconfiguration and biassed for movement to a second configuration, theretainer being held in the first configuration while the valve member isin the first configuration and being releasable from said firstconfiguration, by axial movement of the valve assembly relative to thevalve body, to move the valve member to the open position and retain thevalve member in the open position; and a coupling arrangement includinga retractable coupling member for initially coupling the valve assemblyto the body to prevent relative movement therebetween, wherebyretraction of the coupling member permits uncoupling, and thus permitsrelease of the valve member retainer.
 2. The valve of claim 1, wherein,in the first configuration, the valve member is normally closed and willhold pressure from said one direction but will open in response topressure from the opposite direction.
 3. The valve of claim 1, whereinthe valve member retainer is biassed towards its second configuration bya spring.
 4. The valve of claim 1, wherein the axial movement of thevalve assembly releases a trip coupling.
 5. The valve of claim 1,wherein the axial movement is achieved by application of a pressureforce to the valve member or to a portion of the valve assembly.
 6. Thevalve of claim 4, wherein the pressure force is applied directly in thevalve member by fluid in the valve body.
 7. The valve of claim 1,wherein said axial movement of the valve assembly relative to the bodyis resisted by a biassing member.
 8. The valve of claim 7, wherein thebiassing member is pre-stressed such that the degree of axial movementnecessary to release the valve member retainer is only obtained byapplication of a pressure above a predetermined level.
 9. The valve ofclaim 1, wherein the coupling arrangement includes a shear coupled thatwill release on application of a predetermined force.
 10. The valve ofclaim 1, wherein a coupling member actuator is provided and is remotelyactivatable to permit uncoupling.
 11. The valve of claim 10, wherein thecoupling member actuator is an electric motor.
 12. The valve of claim10, wherein the coupling member actuator is activated by pressurepulses.
 13. The valve of claim 1 wherein the valve assembly includes aportion for initially closing a port in the wall of the body, which portcommunicates with a control line linked to a packer or other fluidactuated downhole tool, the valve assembly portion being movable topermit fluid flow through the port from the body passage.
 14. A downholevalve including:a body defining a flow passage; a valve assembly mountedin the body, the valve assembly including a valve member being movablefrom a first configuration to a second configuration, in the firstconfiguration the valve member preventing flow in at least one directionthrough the passage, and in the second configuration the valve memberbeing retained in an open position; a valve member retainer normallyrestrained in a first configuration and biassed for movement to a secondconfiguration, the retainer being held in the first configuration whilethe valve member is in the first configuration and being releasable fromsaid first configuration, by axial movement of the valve assemblyrelative to the valve body, to move the valve member to the openposition and retain the valve member in the open position; and abiassing member for resisting said axial movement of the valve assemblyrelative to the body.
 15. A downhole valve including:a body defining aflow passage; a valve assembly mounted in the body, the valve assemblyincluding (a) a valve member being movable from a first configuration toa second configuration, in the first configuration the valve memberpreventing flow in at least one direction through the passage, and inthe second configuration the valve member being retained in an openposition, (b) a portion for initially closing a port in the wall of thebody, which port communicates with a control line linked to a packer orother fluid actuated downhole too, the valve assembly portion beingmovable to permit fluid flow through the port from the body passage; avalve member retainer normally restrained in a first configuration andbiassed for movement to a second configuration, the retainer being heldin the first configuration while the valve member is in the firstconfiguration and being releasable from said first configuration to movethe valve member to the open position and retain the valve member in theopen position.
 16. The valve of claim 15, wherein the valve memberretainer is releasable from its first configuration by axial movement ofthe valve assembly relative to the valve body.
 17. The valve of claim 1wherein the valve assembly includes a valve member carriage and thereleased retainer is movable relative thereto.
 18. The valve of claim17, wherein the valve member is a ball and the carriage includes a ballcage and the retainer is movable relative to the cage, following releaseof the retainer from the first configuration.
 19. The valve of claim 1,wherein the retainer includes an axially movable sleeve defining aportion of the valve flow passage.
 20. The valve of claim 19, whereinthe valve is a ball valve and an end of the sleeve bears on the ballsurface to push the ball to the open position.
 21. The valve of claim19, wherein the valve member is in the form of one or more flappers andan end of the sleeve is utilised to push the flappers to the openposition and then define the flow passage past the flappers.
 22. Thevalve of claim 1 wherein the valve is configurable to permit limitedflow of fluid in said one direction by providing a further valveincluding a normally open valve member which remains open where there isonly a limited flow in said one direction, but closes in response to ahigher rate of flow.
 23. The valve of claim 22, wherein said furthervalve includes a valve member which is normally lifted from its seat bya spring, such that fluid may pass around the member, a higher flowcreating a pressure force on the valve member and overcoming the springforce to close the valve.
 24. The valve of claim 22, wherein saidfurther valve is provided in the valve member of said valve assembly.25. The valve of claim 1 further comprising means for equalisingpressure across the valve member, said means defining a fluid path forproviding fluid communication across the valve member following releaseof said valve member retainer from the first configuration.
 26. Adownhole check valve comprising:a body defining a flow passage and; avalve assembly mounted in the body, the valve assembly including: aprimary valve member being movable from a first configuration to asecond configuration, in the first configuration the valve memberpreventing flow in at least one direction through the passage, and inthe second configuration the valve member being retained in an openposition; and a normally open secondary valve member configured topermit flow in said one direction through said primary valve member upto a predetermined rate and being closed by fluid forces in the event ofthe flow rate approaching said predetermined rate.
 27. The valve ofclaim 26, wherein the secondary valve member is located on the primaryvalve member and controls flow through a passage extending therethrough.28. Downhole apparatus including:a body; a member mounted on the bodyand being movable relative thereto; a coupling between the body and themember, in a first configuration the coupling preventing movement of themember relative to the body and in a second configuration the couplingpermitting such movement; a coupling actuator for moving the couplingfrom the first to the second configuration; a sensor operativelyassociated with the coupling actuator and for activating the actuator ondetection of a predetermined activation signal, wherein the member formspart of a valve, the valve being locked in a closed first configurationby the coupling and being movable to an open second configuration onre-configuring of the coupling.
 29. The apparatus of claim 28, whereinthe valve controls flow of fluid through an axial passage defined by thebody.
 30. The apparatus of claim 28, wherein the valve controls flow offluid through a wall of the body.
 31. Downhole apparatus including:abody; a member mounted on the body and being movable relative thereto; acoupling between the body and the member, in a first configuration thecoupling preventing movement of the member relative to the body and in asecond configuration the coupling permitting such movement; a couplingactuator for moving the coupling from the first to the secondconfiguration; a sensor operatively associated with the couplingactuator and for activating the actuator on detection of a predeterminedactivation signal, wherein the member is movable by application of fluidpressure thereto.
 32. Downhole apparatus including:a body; a membermounted on the body and being movable relative thereto; a couplingbetween the body and the member, in a first configuration the couplingpreventing movement of the member relative to the body and in a secondconfiguration the coupling permitting such movement; a coupling actuatorfor moving the coupling from the first to the second configuration; asensor operatively associated with the coupling actuator and foractivating the actuator on detection of a predetermined activationsignal, wherein the coupling actuator include an electric motor linkedto a threaded shaft and threaded follower for movement therealong.